Supposedly this "maneuver" was due to a combination of the early seasons using spandex and the actor having back issues (because they sized the costumes too small).
The version of the story I remember is that Jonathan Frakes had a bad back because he used to work as a mover before he made it as an actor. But the costumes almost certainly didn't help matters.
Being 6'3" (190cm) probably made it a whole lot easier to do that, too.
Also I think the last scene in that youtube link is from the 7th season (looks like the admiral from The Pegasus) so I'd hope any uniform issues would be fixed by then.
